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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

79

acid and titrated with N/io-permanganate;   this gives the iron in the
ferrous state (i c.c. N/io-permanganate = 0-0056 gram Fe).

3.  Sulphuric Acid.—The nitrate from the total iron precipitate is
acidified with hydrochloric  acid and precipitated with barium chloride
fi part BaS04 = 0-3433 part S08).

4.  Nitric Acid.—This may be determined by one of the methods given
under " Fertilisers."

5.  Alkalies.—In absence of lime and magnesia (the usual case), it is
sufficient to precipitate the iron with ammonia as in 2, to filter, evaporate
the nitrate to dryness with a few drops of sulphuric acid, and calcine and
weigh the residue :  assuming the latter to be sodium sulphate, the alkalies
are calculated.

NITROBENZENE
C6H5-N02 = 123

This is sold in various qualities : (i) Pure light nitrobenzene (Essence of
mirbane), a colourless or yellowish liquid with a pleasant odour of bitter
almonds, D = 1-208-1-209, b.pt. 205-207°. (2) Crude heavy nitrobenzene
(Nitrobenzene for red], a reddish liquid smelling of bitter almonds and tarry
products, D = 1-18-1-19, b.pt. 210-220° ; it contains hitrotoluenes and
other homologues. (3) Extra heavy nitrobenzene, a brownish-red liquid,
D = 1-167, b.pt. 220-240°, containing little nitrobenzenes and much nitro-
toluenes, nitroxylenes, etc.

With these products the determinations usually made are those of the
specific gravity and the boiling point.

Nitrotoluene may be detected in pure nitrobenzene by shaking a few
c.c. of the product with 1-2 grams of powdered sodium (not potassium)
hydroxide : in presence of nitrotoluene, even in very small amounts, the
liquid becomes brownish yellow.

Pure nitrobenzene should have a' specific gravity not less than 1-20 (at 15°),
and at least 95% of it should distil between 204° and 208°.

POTASSIUM   ALUMINIUM   SULPHATE—see Alum

POTASSIUM   BISULPHITE
KHS08 = 120

This usually forms slightly effloresced crystalline masses, very readily
soluble in water to an acid solution. It may contain the same impurities
as sodium bisulphite and its value depends on its proportion of sulphur
dioxide. Its analysis is carried out similarly to that of the sodium salt-

Commercial potassium bisulphite is also called metabisulphite, and is probably
a mixture of the normal bisulphite, KHSO3, and the metabisulphite, K2S2O5. It
contains about 53% of total SO2-few pieces of copper and cone, sulphuric, add : if nitrate is present, evolu-